The earliest known inhabitants of Moravia were…
796 CE
The earliest known inhabitants of Moravia were the Boii, a Celtic tribe that gave its name to neighboring Bohemia, and the Cotini, another Celtic tribe.
These were succeeded about 15-10 BCE by the Germanic Quadi.
The Germanic peoples were pushed back from the middle Danube by the coming of the Avars in 567.
The exact date of the arrival of the Slavs in Moravia, as in Bohemia, is uncertain; but by the late eighth century Moravia was settled by the Slavs, who acknowledged no particular tribe but took the general name of Moravians from the Morava River.
An important trade route from the Baltic to the Adriatic Sea has developed through the Morava River basin.
When Charlemagne destroys the Avar empire about 796, he rewards the Moravians for their help by giving them a part of it, which they hold as a fief from him.
They thus become loosely tributary to him for all their lands.